Neville , your theory in my opinion would only be valid in the event of no faults being found with the hardware. The MAS incident found a hard fault and resulted in ADIRU mods to eliminate the potential for this. I think these incidents highlight the fact that you cant test for every potential failure, especially in the FBW area. So you can potentially have something waiting for years before the right set of circumstances that no one thought of . Not just FBW but also electrical power , i.e 747-400 water leak and various relay failures on 737/320 over the last few years. Just hope we all learn from these incidents and it improves our system knowledge , so that the guys at the pointy end in the hot seat are able to deal with whatever happens when it doesnt conform to the book .